Can Cycles renders be done from the command line?
Yes you can, This will render a single frame 

blender --background filename.blend --render-output //test_ --engine CYCLES --render-format PNG --use-extension 1 --render-frame 5


This will output a file named test_0005

While experimenting, I more or less substituted CYCLES with the parameters I found here. You can check the link to see what they mean and or do.